Coherent change detection (CCD) offers the capability for detecting changes that occur in a target scene between SAR imaging passes. A sequence of SAR imaging passes produces a sequence of complex SAR images that respectively correspond to the imaging passes. The CCD process produces a set of CCD products, each of which represents a comparison of a pair of SAR images of the target scene that have been captured during time-wise adjacent airborne imaging passes. The creation of each CCD product involves a sub-pixel co-registration of the associated pair of SAR images. The set of CCD products is then registered to a common coordinate system, resulting in a set of co-registered CCD products for use in producing statistical models about the target scene, on a pixel-by-pixel basis. Traditionally, however, for a large set of SAR images taken across a long span of time, it has been difficult to produce a co-registered set of CCD products with sufficient accuracy to permit collection of useful statistics.
In particular, extending the aforementioned pair-wise, sub-pixel co-registration approach across many images presents some problems. First, every time an image is transformed a small amount of error is introduced. Second, creating a good CCD product requires very accurate sub-pixel registration. Accurate sub-pixel registration cannot be achieved with complex SAR images that are significantly separated in time, which leads to poor quality CCD products. These problems make it difficult to use simple solutions such as registering all of the CCD products to a common coordinate system.
It is desirable in view of the foregoing to provide for producing a set of co-registered CCD products that is suitable for statistical analysis and avoids problems such as those associated with longer image sequences and increased time between image passes.